A fast-response and highly linear humidity sensor based on quartz crystal microbalance

Fig. 1 Response and recovery times of the humidity sensor. [Display omitted] •Polyvinyl alcohol and nano-silica composites are used as the sensing film of humidity sensor.•The preparation of sensitive film is simple.•The prepared humidity sensor has short response time (5 s) and short recovery time (21 s).•The frequency shifts linearly respond to the relative humidity (R2 = 0.9990). A fast-response and highly linear humidity sensor based on quartz crystal microbalance (QCM) was prepared by using polyvinyl alcohol (PVA) and nano-silica composites as sensing film. The mass ratio of PVA to nano-silica and the total mass of sensing film which can significantly influence the response time and linearity of humidity sensor were well discussed. The results show that the optimal mass ratio of PVA to nano-silica is 1:1.5 and the total mass of the sensing film coated on the surface of QCM is 1.0 μg. Under the optimum conditions, the frequency shifts linearly respond to the relative humidity. The prepared humidity sensor has short response time (5 s), short recovery time (21 s), good stability and reproducibility. The developed humidity sensor is expected to be used for the detection of humidity in practice.